1. Field of the Invention
The present invention relates generally to the field of load cell mounts.
2. Description of the Background Art
Scales are devices that are used to determine a weight of an object by measuring the gravitational pull exerted on that object. Scales are commonly used to determine the physical amount or quantity of an item, such as a foodstuff, for example. Scales are therefore a necessary component of commerce, and aid in the smooth flow of commerce by ensuring fairness and accuracy in any transactions requiring a weight or amount measurement.
Modern scales have benefitted greatly from improvements in technology. One device that has revolutionized scales is the load cell. Load cells are widely used in scales designed to weigh large quantities, such as scales for weighing trucks, train cars, tanks, hoppers, or other large loads or machinery. A load cell is a piece of steel that contains a strain gauge. The strain gauge is an electronic transducer that changes resistance when it is stressed. It measures a strain imposed on the load cell by measuring an almost imperceptible deformation of the load cell under a load. Typically, in a load cell multiple strain gauges are connected in a Wheatstone bridge configuration. When an input voltage is applied to the bridge, the bridge outputs a voltage proportional to the force on the load cell. By varying the size and strength of the steel comprising the load cell body, the load cell can be designed to accommodate different load capacities.
One type of load cell is a shear or shear beam type (also referred to as compression type) load cell. This type of load cell is a device that is placed horizontally under a load, with the force of the scale directed onto a small area, or "sweet spot," on the top of the load cell.
In use, multiple load cells may be used in a scale application. Multiple load cells may be placed under a weigh bridge of a scale, and the outputs of all load cells may be summed to provide a total weight of the weight bridge and load.
Load cells offer several advantages over the traditional mechanical scale apparatus. Because load cells are electronic, they can provide an electronic output and can be calibrated electronically, with no moving parts to wear out. Load cells are resistant to dirt and moisture.
In scale applications, load cells are only a component, and must be mounted within the scale so as to receive the full weight of the scale and the load. In order to generate accurate readings, the weight must be imparted to the load cell with only a vertical force component, and with no horizontal force component. This means that any horizontal motion or sway must be reduced or eliminated. One of the biggest drawbacks of related art load cell mounts is the inability to accommodate and minimize motion of the weigh bridge relative to the load cell. In related art load cell mounts, external devices were employed in order to limit or reduce sway of the weigh bridge due to movement of a vehicle onto the weigh bridge. These external devices often took the form of bumpers that limited sway. In an effort to solve this problem, one related art mount employed a pivoting mount that pivoted on the top surface of the load cell (U.S. Pat. No. 4,549,622 to Leiman). Unfortunately, the Leiman load cell mount thereby imparted a torsional force to the load cell, with the resulting torsional force affecting the accuracy of measurements.
There remains a need in the art for improvements in load cell mounts.